Q40 / 57 · KVPY 2019 (SA) · Physics
Consider two equivalent, triangular hollow prisms A and B made of thin glass plates and arranged with negligible spacing as shown in the figure. A beam of white light is incident on prism A from the left. Given that, the refractive index of water is inversely related to temperature, the beam to the right of prism B would not appear white, if
Consider two equivalent, triangular hollow prisms A and B made of thin glass plates and arranged with negligible spacing as shown in the figure. A beam of white light is incident on prism A from the left. Given that, the refractive index of water is inversely related to temperature, the beam to the right of prism B would not appear white, if
- Aboth prisms are filled with hot water
- Bboth prisms are filled with cold water
- Cboth prisms are empty
- Correct answerDprism A is filled with hot water and prism B with cold water
Solution
Prism B is inverted relative to prism A. So, dispersion of light caused by prism A and B is in opposite direction.
If bending of light caused by B is less than or more than that of A, then out going beam of light is not white. So, when both prism are filled with water at different temperatures, their refractive indices are different and the dispersion produced by A and B are not equal and opposite. Hence, with condition in
(d) beam to right of prism B will be coloured.
Hence, the correct answer is option: 'D'.